Fluid power generator

ABSTRACT

In a fluid power generator system using operative fluid energy, a measured tip speed ratio and a reference tip speed ratio are compared with each other. If the measured tip speed ratio is smaller than the reference tip speed ratio, a generator is placed in a no-load state, thereby restoring the number of rotations of the wing axial shaft to the number of rotations corresponding to the reference tip speed ratio. Further, the operation of the generator is controlled on the basis of the tip speed ratio calculated from the flow rate of the fluid, thereby providing a maximum output for each flow rate. In this way, a change in the flow rate and number of rotations can be appropriately dealt with and the maximum output for each flow rate of the operative fluid can be dealt with, thereby increasing a quantity of generated power.

TECHNICAL FIELD

[0001] This invention relates to a fluid power generator system forconverting operative fluid energy such as wind into rotary energy to beused as electric energy.

BACKGROUND ART

[0002] As a fluid power generator system which uses the operative fluidenergy as a driving source to generate electric power, a wind vanegenerator using wind power energy has been proposed. In the field ofthis wind vane generator, the wind power energy, a demand of using windpower energy in a wide range from a breeze to strong wind has beenenhanced.

[0003] The wind power generator system includes a generator which isdriven by rotation of a wind turbine and a battery which is charged bypower supply from the generator. In this wind power generator system,power can be supplied to loads such as an electric device while thebattery is charged by the rotation of the wind turbine.

[0004] In the above conventional wind power generator system, even whenthere is a breeze blowing, the generator which serves as load for thewind turbine remains in a coupled state. Namely, the wind powergenerator system does not have a function of automatically decouplingthe generator according to a change in the wind and coupling the windturbine after the rotation of the wind turbine has been restored.

[0005] Where there is strong wind when the battery is in a full-chargedstate, the wind turbine is mechanically braked or the output from thegenerator is short-circuited to stop power generation,. therebypreventing excessive rotation of the wind turbine. However, the momentthat the output from the generator is short-circuited, the generator maybecome no load and the rotation of the wind turbine may becomeexcessive.

[0006] An object of this invention is to provide a fluid power generatorsystem which can deal with changes in the flow rate of an operativefluid such as wind and number of rotations (rotational speed) bycontrolling the tip speed ratio of a generator, thereby acquiring amaximum output at a specific flow rate.

DISCLOSURE OF THE INVENTION

[0007] In order to attain the above object, in accordance with thisinvention, there is provided a fluid power generator system comprising agenerator coupled with a wing axial shaft which is rotated by operativefluid energy as a driving source and a load device including a batteryconnected to the generator, comprising a comparing means for comparingan measured tip speed ratio and a reference tip speed ratio, themeasured tip speed ratio being calculated by a flow-rate signal based ona flow-rate of the operative fluid and a number of rotations signalbased on the number of rotations of the wing axial shaft, and thereference tip speed ratio providing a maximum conversion efficiency ofthe operative fluid energy in the fluid power generator system; and

[0008] a load control means for on/off controlling the load device sothat if the measured tip speed ratio is smaller than the reference tipspeed ratio as a result of comparison by the comparing means, thegenerator is placed in a no-load state, thereby restoring the number ofrotations of the wing axial shaft to the number of rotationscorresponding to the reference tip speed ratio.

[0009] Preferably, the load control means places the generator in theno-load state if the measured tip speed ratio is smaller than thereference tip speed ratio as a result of comparison by the comparingmeans and continues the no-load state until the number of rotations isrestored to the number of rotations corresponding to the reference tipspeed ratio, thereby dealing with a change in the number of rotations ofthe wind axial shaft.

[0010] Preferably, when the battery of the load device is fully charged,power supply to the battery is stopped by an output from an excessivevoltage detecting unit and a dummy load is connected to the generator.

[0011] Further, there is provided a fluid power generator systemcomprising a generator coupled with a wing axial shaft which is rotatedby operative fluid energy as a driving source, comprising a controlmeans for controlling the operation of the generator on the basis of ameasured tip speed ratio which is calculated by a measured flow-rate ofthe operative fluid and a measured number of rotations of the wing axialshaft, thereby providing a maximum output for a specific flow-rate ofthe operative fluid..

[0012] Preferably, the control means constantly controls the operationof the generator on the basis of a measured tip speed ratio which iscalculated from a measured flow rate of the operative fluid and highernumber of rotations exceeding an output peak value at the measurednumber of rotations of the axial shaft, so that a maximum output for thespecific flow rate of the fluid is obtained by load given to the wingaxial shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a block diagram showing an embodiment of this invention;

[0014]FIG. 2 is a block diagram of a control circuit;

[0015]FIG. 3 is a conceptual view showing a control system;

[0016]FIG. 4 is a characteristic view of power generation efficiencyversus a tip speed ratio; and

[0017]FIG. 5 is a characteristic view showing an example of control ofthe tip speed ratio.

BEST MODE FOR CARRYING OUT THE INVENTION

[0018] Now referring to the drawings, an explanation will be given of anembodiment of this invention.

[0019]FIG. 1 shows an arrangement of the wind power generator whichconverts wind power energy serving as operative fluid energy into rotaryenergy to be used as electric energy;

[0020] In FIG. 1, a wind turbine 1 includes e.g. linear blades 2 whichare integrally attached to a wing axial shaft 4 by upper and lowersupporting blades 3, respectively. The wing rotary shaft 4 is coupledwith a generator 5 such as a synchronous generator (three-phase AC)through a transmission. The wing axial shaft 4 is provided with a brake7 and a revolving number detecting unit 8 for the number of rotations ofthe wind turbine 1.

[0021] The revolving number detecting unit 8 serves to detect the numberof rotations of the wind turbine 1 with the aid of a tachometergenerator and a photosensor and photovoltaic converter. This detectednumber-of-revolution signal is supplied to a control circuit 9. The windspeed is detected by a wind speed detecting unit 10 such as a wind speedindicator, and the detected wind speed signal is supplied to a controlcircuit 9.

[0022]FIG. 2 shows the main portion of the control circuit 9 in FIG. 1.The number of rotations of the wing axial shaft 4 is detected by thenumber of rotations detecting unit 8. The number of rotations signal ofthe wing axial shaft is supplied to a tip speed ratio calculatingcircuit 91 for calculating an measured tip speed ratio in the controlcircuit 9. The wind speed signal detected by the wind speed detectingunit is also supplied to the measured tip speed ratio calculatingcircuit 91.

[0023] The measured tip speed ratio calculating circuit 91 calculatesthe measured tip speed ratio from the number of rotations signal basedon the number of rotations of the wing axial shaft 4 and the wind speedsignal based on the wind speed. The measured tip speed ratio is suppliedto a comparing circuit (comparing means) 92. The comparing circuit 92also receives a reference tip speed ratio. The reference tip speed ratiois previously set at a value where the conversion efficiency of windpower is maximum in the wind power generator system in FIG. 1.

[0024] On the basis of a comparison result between the measured tipspeed ratio and the reference tip speed ratio, the comparing circuit 92supplies a control signal to a load control circuit 96. As a result ofcomparison, if the measured tip speed ratio is smaller than thereference tip speed ratio, the comparing circuit 92 issues a command ofturning off a battery 111 of the load device 11 and an electric contactof the generator 5 to a load control circuit 96. The load controlcircuit 96 causes an exchanger 113 to place the generator 5 in a no-loadstate. The operation of placing the generator 5 in the no-load state canbe easily implemented using an unload valve.

[0025] In this way, if the measured tip speed ratio is smaller than thereference tip speed ratio, the generator 5 is placed in the no-loadstate to reduce the load for the wing axial shaft 4. This operation willbe continued until the number of rotations of the wind axial shaft isrestored to that corresponding to the reference tip speed ratio. Thus,the start of the rotation of the wind turbine 1 is greatly acceleratedso that the wind power generator system can sensitively deal withchanges in the wind speed and number of rotations. This improves thepower generation efficiency and hence the net working rate of the windpower generator system.

[0026] In the load device 11, if the battery 111 is in a fully-chargedstate, in response to the output from an excessive voltage detectingcircuit 112, the exchanger 113 stops the power supply to the battery 111and connects a dummy load 114 to the generator 5. Thus, the generator 5is not placed in the no-load state so that suitable braking is applied.Accordingly, the wing axial shaft 4 coupled with the generator 5, i.e.the wind turbine 1 is prevented from falling into an excessive rotaryrange so that the linear blades 2 of the wind turbine 1 is preventedfrom being damaged. The dummy load 114 may be given by turning on lightsor operating a connected heater for heat recovery. Thus, the surpluspower can be effectively used until the full-charged state of thebattery 111 is dissolved.

[0027] In the embodiment shown in FIG. 1, the operation of each of thegenerators A to G can be controlled on the basis of the tip speed ratioβ (β=number of rotations N or rotor tip speed/ wind speed V) which hasbeen calculated from the wind speed V and the number of rotations N ofthe wind rotary shaft 4. The rotor tip speed is represented by 2πRN (Ris a diameter) Assuming that 2πR is constant, the rotor tip speed can bereplaced by the number of rotations N. Specifically, as shownin FIG. 5,when the generator (e.g. A) is coupled with the wind rotary shaft 13 ata higher number of rotations, i.e. point (b) (β=4.5) exceeding a peakvalue, i.e. point (a) of the wind speed V=9 m/sec., the generator servesas a load for the wind rotary shaft 13. As a result, the number ofrotations N of the wing rotary shaft 13 decreases like ancounterclockwise arrow in FIG. 5 and reaches the peak value, i.e. point(a) of the output.

[0028] Because the maximum efficiency of the wind turbine 1 is actuallyobtained at the tip speed ratio β≈4.5, the operation should be made inthe vicinity of β=4.5. In this way, by controlling each of thegenerators A to G on the tip speed ratio, as seen from FIGS. 5 and 6,these generators A to G can be operated at the peak value, i.e. point(a) so that the maximum output according to a specific wind speed can beobtained.

[0029]FIG. 3 is a conceptual view showing the control system of the windpower generator system shown in FIG. 1. This control system has threefunctions of a start-up and accelerating function, tip speed ratiocontrol function and a braking function. The wind speed is detected by awind speed detecting unit 10 which may be an anemometer. The number ofrotations of the wind turbine 1 is detected by the number of rotationsdetecting unit 8 which includes a tachometer generator and measurementby a photosensor and photovoltaic converter. These wind speed signal andnumber of rotations signal are processed by a voltage comparator 12 anda logic circuit 13 and are produced as control signals.

[0030] The start-up and accelerating function is to operate a startmotor when the wind speed exceeds a certain minimum value and the tipspeed ratio of the wind turbine 1 is lower than a prescribed value. Thetip speed ratio control function is to operate an unload valve to placethe generator in a no-load state when the tip speed ratio is lower thana maximum value. This state continues until the number-of-revolution ofthe wind turbine 1 is restored to the reference number of rotations todeal with a change in the number of rotations.

[0031] The braking function includes two functions inclusive of a normalbraking function and an emergency braking function. The normal brakingfunction is to operate an air brake when the wind speed exceeds adesigned maximum value. The emergency braking function is to operate theair brake when the wind speed exceeds the designed maximum value andalso the detected signals from the two number of rotations detectingunits 8 are abnormal.

[0032] The braking system includes a braking system by a cut-out windspeed and an emergency braking system by excessive rotation by the windturbine 1. Particularly, the braking system has a function ofself-diagnosis for detecting abnormality of the number of rotationswhich is important from the viewpoint of safety.

[0033] This invention should not be limited to the above embodimentwhich has been explained in the wind power generator system. The fluidpower generator system according to this invention can be applied to awater power or other generating system. This invention can beimplemented in combination with solar power generation as a hybrid powergenerator system.

[0034] The fluid power generator system can be equipped with controlmeans which can monitor various observed data indicative of a generatedpower, number of rotations, flow rate, etc. or video data capable ofmonitoring an operating status by using a communication means such assatellite communication or internet on any site on the earth, therebyimplementing the operation in bi-directional communication. On the sidewall of a high building, the axial shaft may be located not verticallybut horizontally. In place of the supporting blade, a disk serving as asupporting portion can be employed.

INDUSTRIAL APPLICABILITY

[0035] In accordance with the invention described in claim 1, in thefluid power generator, a change in the flow-rate and number of rotationscan be appropriately dealt with so that the power generation efficiencycan be improved. This improves the operation efficiency of the fluidpower generator system and increases the generated power.

[0036] In accordance with the invention described in claim 2, when theflow rate becomes lower than the reference level, the generator isautomatically placed in the no-load state so that the burden for thewing axial shaft can be relaxed and the no-load state can be continueduntil the number of rotations is restored to the reference number ofrotations. Therefore, a change in the flow-rate and number of rotationscan be appropriately dealt with so that the power generation efficiency.This improves the operation efficiency of the fluid power generatorsystem and increases the generated power.

[0037] In accordance with the invention described in claim 3, since thebattery is fully charged, power supply to the battery from the generatoris stopped and the dummy load is coupled with the generator. Therefore,the generator is not placed in the no-load state so that suitableelectric braking can be applied. Thus, the rotating unit at high speedrotation can be prevented from being damaged. Further, by using theheater or the like as the dummy load, the surplus power can beeffectively used until the fully-charged state of the battery isreleased.

[0038] In accordance with the invention described in claim 4, bycontrolling the operation of the generator on the basis of the tip speedratio which is calculated from the flow rate and the number ofrotations, the maximum output for each flow rate of the operative fluidcan be obtained. This improves the operation efficiency of the fluidpower generator system and increases the generated power.

[0039] In accordance with the invention described in claim 4, bycontrolling the operation of the generator on the basis of the tip speedratio which is calculated from the flow rate of the operative fluid andthe higher number of rotations exceeding an output peak value at themeasured number of rotations of the axial shaft, the maximum output foreach flow rate of the operative fluid can be obtained. This improves theoperation efficiency of the fluid power generator system and increasesthe generated power.

1. A fluid power generator system comprising a generator coupled with awing axial shaft which is rotated by operative fluid energy as a drivingsource and a load device including a battery connected to the generator,wherein a comparing means for comparing an measured tip speed ratio anda reference tip speed ratio, said measured tip speed ratio beingcalculated by a flow-rate signal based on a flow-rate of the operativefluid and a number of rotations based on the number of rotations of saidwing axial shaft, and said reference tip speed ratio providing a maximumconversion efficiency of the operative fluid energy in said fluid powergenerator system; and a load control means for on/off controlling saidload device so that if said measured tip speed ratio is smaller thansaid reference tip speed ratio as a result of comparison by saidcomparing means, said generator is placed in a no-load state, therebyrestoring the number of rotations of said wing axial shaft to the numberof rotations corresponding to said reference tip speed ratio.
 2. A fluidpower generator system according to claim 1, wherein said load controlmeans places said generator in the no-load state if said measured tipspeed ratio is smaller than said reference tip speed ratio as a resultof comparison by said comparing means and continues the no-load stateuntil said number of rotations is restored to the number of rotationscorresponding to said reference tip speed ratio, thereby dealing with achange in the number of rotations of said wind axial shaft.
 3. A fluidpower generator system according to claim 1 or 2, wherein when thebattery of said load device is fully charged, power supply to saidbattery is stopped by an output from an excessive voltage detecting unitand a dummy load is connected to said generator.
 4. A fluid powergenerator system comprising a generator coupled with a wing axial shaftwhich is rotated by operative fluid energy as a driving source,comprising a control means for controlling the operation of saidgenerator on the basis of a measured tip speed which is calculated by ameasured flow-rate of the operative fluid and a measured number ofrotations of said wing axial shaft, thereby providing a maximum outputfor each flow-rate of the operative fluid.
 5. A fluid power generatorsystem according to claim 4, wherein said control means constantlycontrols the operation of said generator on the basis of a measured tipspeed ratio which is calculated from a measured flow rate of theoperative fluid and higher number of rotations exceeding an output peakvalue at the measured number of rotations of the axial shaft, so that amaximum output for each flow rate of the fluid is obtained by load givento said wing axial shaft.